Well, ideally the 16V is only applied to RAW, not the VCC pin, which would smoke the atmega.The 10K just limits current draw by the LED, to ~(5V-2V)/10K = 0.3mA.That way you're not sucking lots of battery life when using it in a portable device.

so, if you are not worried about batt life, one could use a 330? instead of using the more expensive low power leds if you were to build your own (plus i have lots of 330? R and 12mcd .20mA leds on hand ?

Yes.20mA to get 12mcd - sounds barely viewable after using 4000mcd LEDs!I don't even bother with power LED when I build my free standing arduino-based designs.LEDs elsewhere make it obvious that power has been applied.

will give it a try on my next one i build. 4000mcd, i would be blind, haha. still using the leds to verify pwr is getting to certain places and i haven't made a mistake. i hear you though, 20mA for 12mcd is not a good tradeoff, but i am running these on multirotors so i have 2.2-3+A batts so i am not too concerned about the efficiency, but in other areas i am starting to see how the leds add up, especially if you want to run stuff from a atmega pin where you are really limited

was a fun way to use/see if i could do 0402 only to realize the sparkfun info stated 0402 but used 0603